Fix error using bim.updating_representation for object with material set

Possibly occurred after 4c255cc, but haven't investigated deeper.

@BIMvoice
The error you were reporting about Split Along Edge operator was caused by this issue, should be fixed now too.
See https://jmp.sh/hgJEHsgH

Example error traceback:
```
Error: Python: Traceback (most recent call last):
  File "C\bonsai\bim\ifc.py", line 487, in execute_ifc_operator
    result = getattr(operator, "_execute")(context)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C\bonsai\bim\module\geometry\operator.py", line 541, in _execute
    self.update_obj_mesh_representation(context, obj)
  File "C\bonsai\bim\module\geometry\operator.py", line 666, in update_obj_mesh_representation
    tool.Ifc.link(new_representation, data)
  File "C\bonsai\tool\ifc.py", line 230, in link
    IfcStore.link_element(element, obj)
  File "C\bonsai\bim\ifc.py", line 258, in link_element
    tool.Geometry.get_mesh_props(obj).ifc_definition_id = element.id()
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C\bonsai\tool\geometry.py", line 92, in get_mesh_props
    return mesh.BIMMeshProperties
           ^^^^^^^^^^^^^^^^^^^^^^
ReferenceError: StructRNA of type Mesh has been removed
```

src/bonsai/bonsai/bim/module/geometry/operator.py

@@ -589,6 +589,7 @@ class UpdateRepresentation(bpy.types.Operator, tool.Ifc.Operator):
                     tool.Material.ensure_material_unassigned([element_type])
                 ifcopenshell.api.material.unassign_material(self.file, products=[product])
                 tool.Material.ensure_material_unassigned([product])
+                data = obj.data  # Required after ensure_material_unassigned
             else:
                 # These objects are parametrically based on an axis and should not be modified as a mesh
                 if extrusion := tool.Model.get_extrusion(old_representation):

src/bonsai/bonsai/tool/material.py

@@ -329,7 +329,10 @@ class Material(bonsai.core.tool.Material):
         or some other may be applied now since it's no longer overridden,
         therefore we need to make sure blender materials reflect correct styles.
 
-        Designed to be called after material.unassign_material API call."""
+        Designed to be called after material.unassign_material API call.
+
+        Will reload representations, invalidating existing object data.
+        """
         elements = elements.copy()  # Avoid argument mutation.
         for element in elements[:]:
             if element.is_a("IfcElementType"):